Process of producing a photoelectric tube



Jan. 16, 1940. P. GORLICH I PROCESS 0F PRODUCING A PHOTOELECTRIC TUBE Filed Feb. 25. 1938 Patented Jan. 16, 1940 I ,rnoonss or PRODUCING, A PnofroELEo TRICTUBE lP a ull Giirlich, Dresden, Germany, assignor to i The invention relates to a ducinga photoelectric tube.

It is an object of the invention toproduce a photoelectric tube requiring only small quantities of photoelectric substances to attain a high degree of sensitiveness.

Another object of the inventionis to produce method .of proa photoelectric tube of high sensitiveness in a simple manner andto effect theregulation of the proportions of materials required automatically during the method.

It'is furthermore, an object of the invention to regulate the sensitlveness of the tube duringits production in accordance with the compound from which the deposits in the tube are released in predetermined quantity.

With these and other objects in view, the invention is described in the following specification Y with reference to the accompanying drawing.

The drawing illustrates diagrammatically a de vice which may be employed for practicing the method of the present invention.

In producing a photoelectric tube, according to.

the present method, the'vessel or bulb of the tube is first produced in customary manner and its inner wall is coated in any desired known way with a metal, as for instance, silver or copper.

The improvement of the present method of completing the production of this tube, includes the stepof depositingby vaporization analkali metal in the form of a thin layer upon the inner metal coating of the tube. For this purpose a tubular reservoir connected with the bulb of the tube may' contain a predetermined quantity of .a

compound of the alkali: metal, or acompound ofqalkali metal may be disposed upon a carrier within the tube itself. Upon applying heat to the compound of alkali metal, the alkali metal itself is liberatedfrom the compound in predeter- 40 mined amounts. This step, therefore, will result inthe deposit, and regulation of the deposit, ofa

condensed layer of alkali metal. on the metal coating in the tube. i

When it is desired to leave certain areas in the interior of the tube free of this deposit of alkali metal, the respective areas of the tube may be heated to a temperature preventing the condensation of the vapor of alkalimetal on the respective areas. i

. The method of the invention includesyfurthermore, the step of converting the deposited alkali metal into an oxide without necessarily effecting the oxidation of other metallic deposits in the tube. For this purpose a predetermined amount 5 of oxygen may be introduced into, the tube, or may wzeiss Ikon Aktiengesellschaft, Dresden, Gerthe tube measured by a galvanometer.

rent, the deposition of free alkali metal is terbe generated within the-tube itself; In the first named case, the bulb may be connected with another tubular reservoir within which a compound adapted to release oxygen is disposed.

Upon heating this compound, as for instance, by

applying heat to the reservoir a predetermined quantity of oxygen will be liberated and this quantity is just sufiicient to convert the layer of alkali metal into a photoelectrically active oxide of alkali metal. Preferably caesium is used'as alkali metal which in this described manner is converted into caesium oxide. l i After this. oxide layer has beenproduced free alkali metal is deposited by vaporization upon the oxide. This free alkali metal may be supplied from another reservoir connected with the bulb of "the tube or may be supplie'din other suitable manner. The reservoir containing free al- 'kali metal is heated to cause the alkali metal to be vaporized in which condition it passes into thebulbwof the tube to be deposited therein as a condensate upon the previously produced oxide layer.

The vaporization of the free alkali metal to.

constitute a toplayer onthe deposit of the oxide of alkali metal is continued until a test shows that the maximum sensitiveness of the tube has been attained. l i I i As a simple test the tube may be energized by light, during this last step of depositing the free alkali metal, and the electric current produced by As soon as the galvanometer indicates a maximum curminated. i l In the drawing the bulb l of the photoelectric tube is connected to the high-vacuum-pump 5 by means of a pipe line 2, 3, and 4. -Before starting 1 the high-vacuum-pump a so called initial or rough vacuumis produced in the bulb I by con- 40 meeting the pipe line to a rough vacuum-pump 1 (notshown). Then before starting the electrically heated high-vacuum-pump 5 the cooks 1 and. 8 must be closed. .After starting the highvacuum-pump thecock 9 is opened and the bulb I is exhausted to an extremely high vacuum. Then the reservoir l0, containing a photoelectrically active metal e. g. caesium, isheated by means of 0 a gas burner or electrically in any known manner. the branch line H into the bulb I. The heating may also be effected in such manner, thatuonly a portion of the caesium in the reservoir is vaporized and passed into the bulb l. After opening the cock l2 the reservoir I3, containing a substance The caesium evaporates and passes over 50 giving ofi oxygen e. g. caesium-permanganate, is

heated until the pressure gauge indicates that the necessary quantity of oxygen has been generated for transforming the metallic caesium layother than oxygen are, prevented from passing into the bulb I. After oxidation the cock 8 is closed and the cock 9 is opened and the bulb I evacuated a second time. Then thereservoir l'l containing e. g. caesium, is heated, to vaporize the alkali metal therein which is deposited on the caesium-oxide layer in the bulb l. After a third evacuation the tube is separated from the pumping device, is sealed, and is now ready for use.

What I claim is:

A method of producing a photoelectric active layer in a photoelectric tube which consists of depositing a metal coating on the inner Wall of the bulb of the tube, evacuating said bulb, depositing a coating of an alkali metal on said metal coating, introducing a predetermined amount of oxygen into said bulb just sufficient to convert said alkali metal coating into a photoelectric active oxide of the alkali metal, evacuating the bulb a second time and then depositing a coating of free alkali metal on said layer of alkali metal oxide.

PAUL GGRLICH. 

